Swap Database?

I have two exact databases, one is month end (me1), one is previous day (st1).  I wrote a pretty elaborate report on the month end database and now I'm being asked to provide it mid-month as well so I want to switch from the me1 db to the st1 version.  Same tables, same fields.  Is that even possible?  I can't find a spot anwhere that allows me to change the source.  It doesn't look like I have change path options like when I use PDFs or spreadsheets.  When I try going back to start page it adds in the whole second database, or if I start with the st1 database and then try and open the report workspace, it wants me to close my existing workspace. 

BLARGH. Really hoping I don't have to rewrite the whole report...  Any ideas?